One word that will make others laugh

My best friend had a thing about that word - all you had to do was look at her and say monkey, and she'd get all hysterical. Of course she'd combat that secret power of mine with the weird lower-eyelid twitch that only she and her brother could do, which gave me the shivers and made me hysterical in turn. Most people couldn't even see what she was doing. The sight of both of us hysterical for no apparent reason did, indeed, make everyone laugh. Perhaps a little skittishly, but they were laughing!